iruser: well, it probably is due to low end Coby electronics/firmware used where the USB icon stays displayed even when fully charged. Actually as I understand it [am no battery expert] most modern portable device batteries can be charged/discharged at any time, with no real negative impact on lifespan [though I could be wrong]...

Yeah, I think your best bet is simply to plug the thing in and charge overnight. Wake up the next day and let your kid enjoy some music/movies.